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Atoms
an atoms is the basic particle from which elements are made
structure of an atom
positively charged nucleus (center) , negatively charged out cloud, orbitals w/ electrons.
Atomic Mass
the amount of protons + neutrons.
atomic number
the number of protons in a nucleus
valence electrons
the electrons w/ the highest energy ( the ones on the outside orbital)
chemical bonds
the force of attraction that holds atoms together as a result of the reagargenment of electrons between them.
ions
is an atom or a group of atoms that have an electric charge (ex: Br-1)
ionic bond
is the attraction between two oppositely charged ions
covalent bond
a bond formed when 2 atoms share electrons
polar bond
a covalent bond when the electrons are not being equally shared
nonpolar bond
a covalent bond when the electrons are being shared equally
metallic bond
an attraction between a positive metal ion and surrounding electrons
element
a substance that cannot be broken down into any other substances by chemical or physical means.
molecule
a group of 2 or more atoms held together by chemical bond (s)
chemical formula
Heterogeneous mixtures
you can usually see the different parts and can easily be separated (ex: salad)
homogeneous mixtures
evenly mixed, you can't see the different parts and it is hard to seperate (ex:soy sauce)
physical change
alters the form or appearance of the matter but doesnt turn the substance in the matter into a different substance.
chemical change
a change in matter that produces one or more new substances.
Law of Conservation of Mass
,atter cannot be created or destroyed in any chemical or physical change.
isotopes
atoms of the same element with different number of neutrons [(no charge) ex : uranium-235 and uranium-238 atom ]
reactants
substances that undergo a chemical change
products
the new substances formed from the reactant
exothermic change
energy is released
endothermic change
energy is absorbed
pH scale
range of 0-14 indcates concentration of H+ ions in a solution bases produce 0H- in water (more than seven) acids produce H+ ions in water (less than seven) even amounts of OH- and H+ = water = neutral
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